The present invention relates to a granulating apparatus of a resin composition, and more particularly to a granulating apparatus of a resin composition which has a reduced amount of fine powders generated at a time of a pulverizing step and can reduces a pulverizing time.
For example, an epoxy resin powder coating material is generally produced in accordance with a dry process by melting and mixing respective raw materials and cooling and pulverizing the raw materials. A cooling belt is mainly used for cooling. In the case that the molten and mixed composition is insufficiently cooled, a pulverizing efficiency is reduced, and further in some cases, a target particle diameter can not be obtained. A pulverizer, a victory mill, a ball mill, a jet mill and the like are employed for pulverization, and these are selectively employed in accordance with a nature of the powder and a target particle diameter. In general, in order to increase the pulverizing efficiency, the pulverization is separately performed in a coarse pulverizing step of pulverizing to a size of 5 to 15 mm and a pulverizing step of pulverizing to a target particle diameter.
In general, since the closer to a target particle diameter after a pulverization a particle diameter of a coarse pulverized material is, the shorter a time required for pulverization is, and the narrower a particle size distribution is, the more a generation of a pulverized powder due to an excessive pulverization can be restricted. However, in the case of using a pulverizer such as a hammer mill or the like, an average particle diameter becomes large in 2 to 5 mm, and a particle size distribution becomes wide in some xcexcm to ten and some mm. A pulverizing time is increased in the case of pulverizing the coarse pulverized material, and a lot of fine powders and coarse powders are generated. In order to improve a yield, it is necessary to again pulverize the fine powders and the coarse powders after recovery and treatment, and this causes an increase of processing cost. That is, since a lot of fine powders and coarse powders are generated in the case that the particle size before the pulverization is coarser than the target particle size distribution and the particle size distribution is wide, a pulverizing efficiency is reduced and a cost becomes high. In particular, the generation of the fine powders involves a deterioration of an operation environment.
A producing method with respect to an improvement of a pulverizing efficiency is disclosed in Japanese Patent Unexamined Publication Nos. 8-218643 and 8-294916. By employing this method, it is possible to reduce an amount of generated fine powders more than the conventional fine pulverizing step using the coarse pulverizing step such as a hammer mill or the like. However, in the case of supplying the molten and mixed resin with using no heating means as in this method, the resin is cooled and becomes a high viscosity during the granulating operation in some nature of the resin, so that a clogging is generated, whereby not only a deterioration of characteristic is generated but also a size of an obtained product is uneven and larger than the target particle diameter even in the case of being granulated. For example, in the case of a pin type disc, when the supplied resin has a low melting viscosity and is continuously supplied to a rotor linearly, the resin is extended between two adjacent pins due to a centrifugal force so as to become a fiber shape, so that a length of the fiber becomes longer than a distance between the pins.
In the case of reducing the distance between the pins in order to reduce the length of the fiber, since an amount of resin between the pins is reduced, an applied centrifugal force is reduced, and the resin is hard to be moved apart from the portion between the pins and stays within the rotor. In order to increase the centrifugal force for preventing the resin from staying, it is necessary to increase a rotational speed, a great power is required and a safety of operation is reduced. On the contrary, since a thickness of the fiber is dependent upon a supply amount of resin, the fiber becomes thin when the supply amount is sufficiently small, however, a diameter of the fiber becomes thick in the case of increasing the supply amount for increasing a production capacity, so that the granulating operation can not be stably obtained.
Further, in the case that the melting viscosity of the supplied resin composition is high and the resin is discontinuously supplied to the rotor since the resin can not be continuously supplied linearly, the resin is supplied to a local pin. Accordingly, the resin is excessively supplied in a local manner and the resin is extruded from a whole of a hollow portion of the pin, the resin forms an uneven shape and a significantly large shape. This can be applied to a vane type disc in the same manner. That is, this method is insufficient to stably obtain the granulating operation which can reduce the pulverizing time.
Conventionally, as a producing method utilizing a rotor, there are listed up Japanese Patent Unexamined Publication Nos. 50-121529, 50-121530, 59-203448 and the like, however, all of them aim to produce a cotton-like product and are different from the present invention.
Further, as a structure of aiming to provide a granulating apparatus of a pulverized coating material, there are listed up Japanese Patent Unexamined Publication Nos. 10-032581, 10-032582 and 10-032583, however, in these manufacturing methods, a container for collecting the granulated powder is structured such that an outer tank is arranged in a vertical direction to a flying direction of granulated powders or a fiber-like resin composition. In this case, since a wall surface receives an impact energy corresponding to a velocity energy of the granulated powders without being reduced, the granulated powders are easily attached to the wall surface. Since a wind stream generated by a rotation of the rotor is applied in a direction of pressing the granulated powders to the wall surface, the granulated powders are easily stayed near the wall surface. Further, since the flying speed of the granulated powders is sufficiently large, a reflecting direction after colliding with the wall surface is substantially the same as an incident direction. Accordingly, a collision with the granulated powders later flying is performed at a high probability, and since the granulated powders are molten and attached to each other, a heat capacity is increased and the granulated powders are easily attached to the wall surface. Once the granulated powders are attached to the wall surface, the granulated powders are further molten and attached to each other on the basis of those granulated powders, so that the granulated powders are hard to be cooled, thereby promoting a deterioration due to a heat.
As a structure of aiming to provide a granulating apparatus of a resin composition for solving the problems mentioned above, there is listed up Japanese Patent Unexamined Publication No. 11-309713. However, there is a case that the granulated powders immediately collected within an outer tank or in a container from the outer tank are cooled at a time of flying in an outer peripheral portion but keep heat in an inner portion. Then, there is a case that the granulated powders are molten and attached to each other and a characteristic is deteriorated in the case of accumulating the granulated powders mentioned above.
An object of the present invention is to provide a granulating apparatus of a pulverized coating material which can reduce a pulverizing time by stably obtaining granulated powders having a particle diameter closer to a target product particle diameter with generating no deterioration of a characteristic, and can reduce a number of classifying steps and save labor and time by reducing a generating amount of fined powders and coarse powders in the pulverizing step.
That is, in accordance with the present invention, there is provided a granulating apparatus of a resin composition comprising:
a cylinder body placed in an upper portion of a rotating rotor;
an opening portion for supplying a resin composition molten and mixed through the cylinder body;
a cylinder having small holes on an outer periphery of the rotor;
heating means;
the small holes on the cylinder being evenly heated passing the resin composition therethrough due to a centrifugal force so as to granulate the resin composition into powders or a fiber shape;
an outer tank recovering the granulated powder and having a wall surface of a granulated powder collision portion inclined at a degree between 10 and 80 degrees; and
a cooling jacket provided on an outer periphery of the outer tank,
wherein a discharge port for taking out the granulated powders is provided in a lower portion of the outer tank, and the granulated powder is transferred from the outer tank while being air cooled by an air feeding apparatus provided in front of the discharge port.